Diseases and conditions often affect people's health, and tests need to be performed to determine the existence and severity of the disease or condition. Conventional test methods use an assay device such as a biomedical test strip to test specimens such as blood, saliva or urine. The assay device is manufactured with an antibody-antigen reaction substance and changes color to present a test result. The antibody-antigen reaction substance may be a probe protein corresponding to a target protein and is mounted on the biomedical test strip. The protein probe bonds to the target protein and changes color when the specimen containing the target protein is biomedical test strip. Consequently, the test result is determined by variation in color of the biomedical test strip.
Many years ago, people observed color variation of the biomedical test strip to determine the test results. However, precision of the test result depended on accuracy of an individual's observation, and inaccuracy of test results were not uncommon.
Therefore, light detectors such as photo diodes, complementary metal-oxide-semiconductors and charge-coupled devices are used now in assay devices to detect changes in color of light to obtain consistent test results.
A conventional automatic assay device was developed to overcome the inconsistency of human observation and comprises an assay device and a biomedical test strip. The assay device has a top surface, a slot and a light detector. The slot is formed in the top surface of the assay device. The light detector is mounted in the slot. The biomedical test strip is mounted removably in the slot over the light detector. However, ambient light may shine on the light detector and cause erratic results.